Factbox: The four men charged in U.S. probe of Trump-Russia ties

(Reuters) - Michael Flynn's plea of guilty on Friday to lying to the Federal Bureau of Investigation made him the fourth person known to be charged in a U.S. Justice Department investigation of ties between President Donald Trump's 2016 election campaign and Russia.

The other three known to be charged by Special Counsel Robert Mueller's probe are: Former Trump Campaign Manager Paul Manafort and Robert Gates. A grand jury in October indicted Manafort, a longtime Republican political consultant, and Gates, a business associate. The two men pleaded not guilty on Oct. 30 to the 12-count indictment, whose charges include conspiracy to launder money, conspiracy against the United States and failing to register as foreign agents of Ukraine's former pro-Russian government. Manafort has agreed to an $11.65 million bail deal that would result in his release from house arrest and electronic monitoring. Former Trump campaign adviser George Papadopoulos. Papadopoulos, a Chicago-based international energy lawyer, pleaded guilty on Oct. 30 to lying to FBI agents about contacts with people who claimed to have ties to top Russian officials. It was the first criminal charge alleging links between the Trump campaign and Russia. White House spokeswoman Sarah Sanders played down Papadopoulos' campaign role, saying it was "extremely limited" and "any actions that he took would have been on his own."